When any common material comes in contact with a biological medium, the biological matter, particularly proteins, deposit on its surface, this phenomenon is called “fouling”. The fouling often deteriorates the function of materials and devices that work in biological media. The problem is especially critical for the materials used in contact with blood serum, plasma, or blood. An effective protection from the fouling is provided by coating the material surface with a layer of an antifouling polymer, such as hydrophilic and electro-neutral poly(oligo(ethylene glycol) methacrylate) (polyHOEGMA), poly(2-hydroxyethyl methacrylate) (polyHEMA), poly(3-hydroxypropyl methacrylate) (polyHPMA), poly(N-(2-hydroxypropyl) methacrylamide) (polyHPMAA), poly(carboxybetaine methacrylate) (polyCBMA), and poly(carboxybetaine acrylamide) (polyCBAA) tethered by one-end to the material surface, the so-called polymer “brush”. The brush is prepared by grafting polymer to or from the surface. The “grafting to” technique consists in synthesizing polymer chains with a functional end-group and subsequent anchoring the chains to the surface containing complementary functional groups via covalent bonding, chemisorption, or physisorption. Much better resistance to the fouling is reached by the “grafting from” technique that consists in anchoring an initiator of living radical polymerization, such as atom transfer radical polymerization (ATRP), or an agent of reversible addition fragmentation transfer polymerization (RAFT) to the material surface. After the addition of a polymerization solution containing monomers, the polymer chains grow from the bound residue of the initiator or the RAFT agent (R) by successive addition of monomer units. The “grafted from” brush is usually characterized by the chemical composition determined by reflection IR spectroscopy or XPS and by the thickness measured by ellipsometry or AFM. So far, only the brushes of polyCBMA and polyCBAA grafted from a surfaces have reduced the fouling from undiluted blood plasma below 5 ng/cm2, (“ultra-low fouling”) and polyHPMAA brushes have reduced the fouling from blood plasma and other complex biological media below the detection limit of surface plasmon resonance (SPR) biosensors. Bioactive substances can be attached to the polymer brushes by covalent bonding to chemically activated functional groups present in the brush. The functional groups may include carboxyl groups in the zwitterionic betaine side chains of polyCBMA and polyCBAA comprising quarternary ammonium cation and carboxylate anion or hydroxy terminal groups of side chains the other antifouling polymers. Carboxy groups are converted by succinimide/carbodiimide (NHS/EDC) chemistry to active NHS-ester and bioactive substances are subsequently attached via covalent bond of amino groups contained in their structure. The NHS/EDC activation worsens recognizably the antifouling properties of polyCBMA and polyCBAA brushes, while any activation of hydroxyl groups leads to the formation of products that impair significantly the antifouling properties of the other brushes. In many applications, the function of the polymer brush coating consists in selective capturing a target biological compound by specific bioactive (in this case “biorecognition”) substances immobilized in the brush. Bioanalytical devices, such as biosensors, designed for direct (so-called “in real-time” or “label-free”) detection of analytes are not able to distinguish specific response to the capturing of target analytes from response to nonspecific fouling from the analyzed medium. Thus increasing the number of immobilized biorecognition substances and decreasing the fouling is of great importance for the detection of analytes present at low concentration in complex biological media, particularly in blood plasma and/or serum.
Preparation and activation of the polymer brushes comprising polyCBMA and polyCBAA are disclosed in the documents US20140370567 and US20130244249. The brushes described in these documents do not comprise the copolymer of N-(2-hydroxypropyl) methacrylamide and carboxybetaine methacrylamide.